In this letter, a reconfigurable dual-polarized broadband antenna with beam-steering capabilities using a parasitic layer is proposed for 5G new radio (NR) frequency range 1 (FR-1) applications. The antenna is a dual-port aperture-stacked patch structure with symmetrical orthogonal (horizontal and vertical) currents. The beam-steering is achieved by a pair of reconfigurable cross-shaped parasitic strips, which bestow the antenna three main beam directions θ = { ~ -25 ^° ,0 ^° , ~ 25 ^° }, Ψ = {0 ^° } with pointing and gain ($ 7$ dB) stability across a 30% impedance bandwidth (S ₁₁ , S ₂₂ <; -10 dB) from 3.2 - 4.3 GHz for both ports/polarizations. A prototype of the antenna is manufactured and measured demonstrating results in accordance with simulation expectations.

One challenge in designing RF wireless bioelectronic devices is the impact of the interaction between electromagnetic waves and host body tissues on far-field wireless performance. In this article, we investigate a peculiar phenomenon of implantable RF wireless devices within a small-scale host body related to the deformation of the directivity pattern. Radiation measurements of subcutaneously implanted antennas within rodent cadavers show that the direction of maximum radiation is not always identical with the direction to the closest body–air interface, as one would expect in larger-scale host bodies. For an implanted antenna in the back of a mouse, we observed the maximum directivity in the ventral direction with 4.6 dB greater gain compared to the nearest body-air interface direction. Analytic analysis within small-scale spherical body phantoms identifies two main factors for these results: the limited absorption losses due to the small body size relative to the operating wavelength and the high permittivity of the biological tissues of the host body. Due to these effects, the entire body acts as a dielectric resonator antenna, leading to deformations of the directivity pattern. These results are confirmed with the practical example of a wirelessly powered 2.4-GHz optogenetic implant, demonstrating the significance of the judicious placement of external antennas to take advantage of the deformation of the implanted antenna pattern. These findings emphasize the importance of carefully designing implantable RF wireless devices based on their placements and relative electrical dimensions in small-scale animal models.

A low complexity reconfigurable antenna (RA) capable of steering its beam into nine different directions corresponding to $\theta=\{-42^{\circ},0^{\circ},42^{\circ}\}$ in the $\phi=\{25^{\circ},0^{\circ},155^{\circ}\}$ planes, and $\theta=\pm25^{\circ}$ in the $\phi=90^{\circ}$ plane, using a reduced number of switches is presented. The RA operating at $3.4 - 3.8$ GHz consists of a central dipole element excited by a coaxial probe, surrounded by four switchable parasitic dipoles located at different height levels above a ground plane which act as either reflector for the elements located at an upper layer or director for the ones at a lower layer, improving the radiation characteristics of the antenna. Each parasitic dipole is fed with a PIN diode as switch which enables the activation of these elements providing the desired modes of operation. The presented RA was manufactured and measured showing results with a good agreement with the theoretical and numerical simulation.

Nonlinear effects in the radio front-end can degrade communication quality and system performance. In this paper we present a new design technique for reconfigurable antennas that minimizes the nonlinear distortion and maximizes power efficiency through the minimization of the coupling between the internal switching ports and the external feeding ports. As a nonlinear design and validation instance, we present the nonlinear characterization up to 50 GHz of a PIN diode commonly used as a switch for reconfigurable devices in the microwave band. Nonlinear models are extracted through X-parameter measurements supported by accurate calibration and de-embedding procedures. Nonlinear switch models are validated by S-parameter measurements in the low power signal regime and by harmonic measurements in the large-signal regime and are further used to predict the measured nonlinearities of a reconfigurable antenna. These models have the desired particularity of being integrated straightforwardly in the internal multi-port method formulation, which is used and extended to account for the power induced on the switching elements. A new figure of merit for the design of reconfigurable antennas is introduced—the power margin, that is, the power difference between the fed port and the switching elements, which combined with the nonlinear load models directly translates into nonlinearities and power-efficiency-related metrics. Therefore, beyond traditional antenna aspects such as port match, gain, and beam orientation, switch power criteria are included in the design methodology. Guidelines for the design of reconfigurable antennas and parasitic layers of minimum nonlinearity are provided as well as the inherent trade-offs. A particular antenna design suitable for 5G communications in the 3.5 GHz band is presented according to these guidelines, in which the specific switching states for a set of target performance metrics are obtained via a balancing of the available figures of merit with multi-objective separation criteria, which enables good control of the various design trade-offs. Average Error Vector Magnitude (EVM) and power efficiency improvement of 12 and 6 dB, respectively, are obtained with the application of this design approach. In summary, this paper introduces a new framework for the nonlinear modeling and design of reconfigurable antennas and provides a set of general-purpose tools applicable in cases beyond those used as examples and validation in this work. Additionally, the use of these models and guidelines is presented, demonstrating one of the most appealing advantages of the reconfigurable parasitic layer approach, their low nonlinearity.

This paper describes the design and validation by simulation of compact dual-port reconfigurable antennas (via switches) providing antenna diversity or port duplexing, which in turn are useful in advanced techniques such as cognitive radio (CR) and Multiple-Input Multiple-Output (MIMO). The design results from optimization of an initial structure using the Genetic Algorithm (GA) and evaluated via Method of Moments (MoM) electromagnetic simulation. The optimization process determines concurrently: antenna geometry, location, number and state of the switching devices. The starting point is a simple planar antenna that offers robustness, compactness and allows for an easy fabrication. The resulting devices operate over a band of 0.6 octaves and possess dimensions under 0.25λ0 × 0.25λ0 for the lowest frequency of operation.